Thursday, November 13, 2014

The lander
successfully touched down on the comet at 10:35 am EST (Eastern Time Zone
encompassing 17 U.S. states in the eastern part of the contiguous United
States, parts of eastern Canada and three countries in Central America – which
is 5 hours behind Coordinated Universal Time [UTC]) on Wednesday, Nov. 12.
right on schedule!.... It took Philae 7 hours to descend to the comet's surface
- one of the most difficult manoeuvres tried in space ~ and after those tense 7
hours, the scientists at the ESA and NASA started celebrating the historic
touchdown of Philae lander. The signal
broke a seven-hour wait of agonising intensity and sparked scenes of jubilation
at the European Space Agency’s mission control in Darmstadt. The team in charge
of the Rosetta mission achieved what at times seemed an impossible task by
landing a robotic spacecraft on a comet for the first time in history.

But celebrations were
tempered by the later discovery that the probe’s two harpoons had not fired to
fasten the craft down in the ultra-low gravity. Scientists now think the probe
may have bounced after first coming into contact with the surface. Ulamec said:
“Maybe today we didn’t just land once, we landed twice.” The safe, if
precarious, touchdown of the lander gives scientists a unique chance to ride
onboard a comet and study from the surface what happens as its activity ramps
up as it gets closer to the sun. Google
too celebrates it with a nice doodle ….

Philae, the
first probe that humans have ever landed on a comet, is already sending back
images from its journey. Philae is a robotic European Space Agency lander that
accompanied the Rosetta spacecraft until its designated
landing on Comet 67P/Churyumov–Gerasimenko, more than ten years after departing
Earth. On 12th November 2014,
the lander achieved the first-ever controlled touchdown on a comet nucleus. Its
instruments are expected to obtain the first images from a comet's surface and
make the first in situ analysis to determine its composition.

The lander is named after
Philae Island in the Nile, where an obelisk was found and used, along with the Rosetta
Stone, to decipher Egyptian hieroglyphics. Philae's
mission is to land successfully on the surface of a comet, attach itself, and
transmit data from the surface about the comet's composition. The scientific
goals of the mission focus on "elemental, isotopic, molecular and
mineralogical composition of the cometary material, the characterization of
physical properties of the surface and subsurface material, the large-scale
structure and the magnetic and plasma environment of the nucleus.

The £1bn ($1.58bn) Rosetta
mission aims to unlock the mysteries of comets, made from ancient material that
predates the birth of the solar system. In the data Rosetta and Philae collect,
researchers hope to learn more of how the solar system formed and how comets
carried water and complex organics to the planets, preparing the stage for life
on Earth. Space agencies have sent probes to comets before, but not like this.
In 1986, Nasa’s Ice mission flew through the tail of Halley’s comet. In 2005,
the agency’s Deep Impact spacecraft fired a massive copper block at comet
Temple 1. But none before now has landed.

The feat marks a profound
success for the European Space Agency (ESA), which launched the Rosetta
spacecraft more than 10 years ago from its Kourou spaceport in French Guiana.
Since blasting off in March 2004, Rosetta and its lander Philae have travelled
more than 6bn kilometres to catch up with the comet, which orbits the sun at
speeds up to 135,000km/h. “Comets are
the original source of Earth’s water. That wee lander is now in position,
poised to re-write what we know about ourselves,” tweeted Chris Hadfield, the
former Canadian astronaut and commander of the International Space Station.

Landing
Philae on the comet’s surface was never going to be easy. When ESA managers got
their first close-up of the comet in July, its unusual rubber duck shape left
some fearing that a safe touchdown was impossible. The shape was not the only
problem. The comet’s surface was hostile: hills and spectacular jutting cliffs
gave way to cratered plains strewn with boulders. If Philae landed on anything
other than even ground it could topple over, leaving it stranded and defunct. Rosetta
spent weeks flying around the comet to create a surface map from which mission
controllers could choose a landing site. From a shortlist of five potential landing
spots, scientists and engineers unanimously voted for a 1 sq km region on the
comet’s “head” later named Agilkia. At the start of the mission, ESA officials
had assumed the comet would be potato shaped and rated their chances of a
successful landing at 75%. After seeing the shape and terrain of their target
close up, those odds fell to around 50%, but climbed again as technical staff
learned more about the landing site.For the mission team, the seven-hour
descent, during which Philae fell at walking speed towards the comet’s surface,
was a nail-biting experience. Eventually, the lander separated from its mothership and touched down.

The lander
could continue working until March next year, when the electronics will become
too warm to work properly. Even when Philae packs up, it may still cling on to
the comet, perhaps for several 6.45-year-long laps around the sun, before
enough material erodes from the comet’s surface for the lander to lose its
grip.